Today's conventional hearing aids typically comprise a Digital Signal Processor (DSP) for processing of sound received by the hearing aid for compensation of the users hearing loss. As is well known in the art, the processing of the DSP is controlled by signal processing algorithms having various parameters for adjustment of the actual signal processing performed, such as the gains in each of the frequency channels of a multi-channel hearing aid, corner frequencies or slopes of frequency-selective filter algorithms, parameters controlling knee-points and compression ratios of compressor algorithms, etc.
The flexibility of the DSP is often utilized to provide a plurality of different algorithms with various signal processing parameters. For example, various algorithms may be provided for noise suppression, i.e. attenuation of undesired signals and amplification of desired signals. Desired signals are usually speech or music, and undesired signals can be background speech, restaurant clatter, music (when speech is the desired signal), traffic noise, etc.
The different algorithms and parameters are typically included to provide comfortable and intelligible reproduced sound quality in different categories of sound environments, such as speech, babble speech, restaurant clatter, music, traffic noise, etc.
Audio signals obtained from different sound environments may possess very different characteristics, e.g. average and maximum sound pressure levels (SPLs) and/or frequency content. Therefore, in a hearing aid with a DSP, each category of sound environment may be associated with particular signal processing algorithms with particular settings of signal processing parameters that provide processed sound of optimum signal quality for the category of the sound environment in question.
Consequently, today's DSP based hearing aids are usually provided with a number of different signal processing algorithms, wherein each algorithm is tailored to a particular category of the sound environment and/or particular user preferences. Signal processing parameters are typically determined during an initial fitting session in a dispensers office and programmed into the hearing aid by activating desired algorithms and setting algorithm parameters in a non-volatile memory area of the hearing aid and/or transmitting desired algorithms and algorithm parameter settings to the non-volatile memory area.
Some known hearing aids are capable of automatically classifying the users sound environment into one of a number of categories of the sound environment, such as speech, babble speech, restaurant clatter, music, traffic noise, etc.
Obtained classification results may be utilised in the hearing aid to automatically select signal processing characteristics of the hearing aid, e.g. to automatically switch to the most suitable signal processing algorithm and parameters for the environment category in question. Such a hearing aid will be able to automatically maintain optimum sound quality and/or speech intelligibility for the individual hearing aid user in various categories of sound environments.
US 2007/0140512 A1 and WO 01/76321 disclose examples of classifier approaches.